The unusual oligonucleotide series 2-5A(ppp(5'A2'p)nA where n=2 to greater than or equal to 4) has been implicated in the mechanism of action of interferons and may play a wider role in the control of growth and development. Recently, we have found a novel level of control in the 2-5A system. Levels of the latent endoribonuclease, 2-5A-dependent RNase, increased by 10-fold in mouse JLS-V9R cells with interferon pretreatment. A smaller, approximately 2-fold, increase in the nuclease was found following interferon treatment of Daudi cells, a human lymphoblastoid line. A survey of the effect of interferon on the nuclease levels in various cell types will indicate whether this is a general phenomenon and may provide information on the biological role of the induction. In addition, we will determine whether 2-5A-dependent RNase levels fluctuate with growth and hormone status, during differentiation in mouse embryonal carcinoma and neuroblastoma cells, and in human peripheral blood mononuclear cells from patients with viral infections (herpes viruses) or from systemic lupus erythematosus or immunodeficiency syndrome patients. The assay for 2-5A-dependent RNase is convenient and may provide a diagnostic indicator of viral disease and/or the presence of interferon. To obtain cloned 2-5A-dependent RNase sequences, double-stranded cDNA will be synthesized from fractionated, interferon-induced poly(A)+ RNA from JLS-V9R cells and inserted into plasmid pBR322 and/or lambda gt11 DNA. The recombinant pBR322 clones which contain interferon-induced sequences will be screened by selecting mRNA by hybridization which can be translated into functional nuclease in Xenopus oocytes or in reticulocyte lysate. In the case of the lambda gt11 clones, the expression of the nuclease cDNA in bacteria will be directly monitored in plaques by the radiobinding assay for 2-5A(32P)pCp. Once isolated, the nuclease cDNA will be labeled by nick-translation and used as probe in Northern blots to directly measure the nuclease mRNA levels in the various systems described above. In the long-term, the nuclease cDNA may be used to select the 2-5A-dependent RNase gene(s) from cloned mouse and human gene banks. The nuclease gene(s) may eventually be used to transform interferon-resistant, nuclease negative cells (e.g., NIH 3T3, clone 1) into nuclease positive cells.